The present invention relates generally to a Ni-based alloy electrode material and, more particularly, to a Ni-based sparking plug material for use in an internal combustion engine. Such a sparking plug exhibits improved high-temperature strength and increased resistance to wear due to sparking, when compared to conventional sparking plugs.
Generally, the electrode material of a sparking plug for use in internal combustion engines is required to simultaneously satisfy the demand for high-temperature strength coupled with high resistance to wear, which results from sparking. To meet such a requirement, Ni-based alloy materials are used today, such as for example, a Ni-based alloy disclosed in Japanese Patent Laid-Open No. 2-34735, having a composition containing, by weight, from 3.1 to 5% of Al, from 0.5 to 1.5% of Si, from 0.1 to 0.65% of Mn, and, as necessitated, from 0.1 to 2% of Cr, the balance substantially being Ni and inevitable impurities.
In recent years, remarkable improvements both in performance and output power of internal combustion engines such as automotive engines have been made, resulting in a need for sparking plug electrode materials having high-temperature strength and improved resistance to wear due to sparking. Consequently, there is a need for sparking plug electrodes which will operate under such severe operating conditions. Unfortunately, conventional Ni-based alloy sparking plug electrode materials, including the above-mentioned Ni-based alloy sparking plug electrodes, are unable to perform under such severe conditions, due to their lack of high-temperature strength and low resistance to wear due to sparking. The inability of the conventional sparking plug electrodes combined with a low resistance to wear has greatly reduced the life expectancy of conventional sparking plug electrodes.
As a result of the foregoing problems related to conventional sparking plugs, the present inventors have endeavored to develop a Ni-based alloy sparking plug electrode material with improved strength at high temperature and increased resistance to wear due to sparking.
The inventors have discovered that Ni-based alloy sparking plug electrode materials with improved strength at high temperature, and increased resistance to wear due to sparking, can be developed when the contents by weight of components such as Al, Si, and Mn coupled with the content of Cr, are respectively present in specified concentrations. The inventors have discovered the specified concentrations of the above mentioned components to be as follows:
Al: from 3.1 to about 4.3%,
Si: from 0.5 to about 1.5%,
Mn: from 0.45 to about 0.65%,
Cr: from 1 to 2%, and
C: from 0.002 to 0.01 wt %, as an alloying component.
Additionally, the concentration of at least one of Mg and Ca should be from 0.005 to 0.05%.